Lung cancer is the leading cause of cancer death worldwide, with an estimated 1.2 million new cases diagnosed each year. In lung adenocarcinoma, which is the most common form of lung cancer, patients harboring mutations in the epidermal growth factor receptor (EGFR) constitute between 10-30% of the overall population. It is this segment of patients for whom EGFR inhibitors such as erlotinib or gefitinib can be most effective (Paez et al. Science 2004; Lynch et al. NEJM 2004; Pao et al, PNAS 2004). The most common mutations associated with good response to these inhibitors are deletions within exon 19 (e.g. E740-A750) and point mutations in the activation loop (exon 21, in particular, L858R). Additional somatic mutations identified to date but to a lesser extent include point mutations: G719S, G719C, G719A, L861 and small insertions in Exon 20 (Shigematsu et al JNCI 2005; Fukuoka et al. JCO 2003; Kris et al JAMA 2003 and Shepherd et al NEJM 2004).
While these agents can be effective treatments for the EGFR mutant sub-population, the majority of patients who initially respond develop resistance. The primary mechanism of resistance, observed in approximately 50% of patients, is due to a second mutation (T790M) which occurs at the gatekeeper threonine residue (Kosaka et al CCR 2006; Balak et al CCR 2006 and Engelman et al Science 2007).
Thus, there is a need for compounds that inhibit EGFR T790M.